Hydrophobins are small proteins of from about 100 to 150 amino acids, which are characteristic of filamentous fungi, for example of Schizophyllum commune. They generally have 8 cysteine units.
Hydrophobins have a marked affinity for interfaces and are therefore suitable for coating surfaces, for example in order to alter the properties of the interfaces by forming amphiphatic membranes. For example, Teflon can be coated by means of hydrophobins to obtain a hydrophilic surface.
Hydrophobins can be isolated from natural sources. Moreover, production processes for hydrophobins and their derivatives are known. For example, German patent application DE 10 2005 007 480 discloses a production process for hydrophobins and derivatives thereof.
The prior art has already proposed the use of hydrophobins for various applications.
WO 96/41882 proposes the use of hydrophobins as emulsifiers, thickeners, surface-active substances, for hydrophilizing hydrophobic surfaces, for improving the water resistance of hydrophilic substrates, for producing oil-in-water emulsions or water-in-oil emulsions. Also proposed are pharmaceutical applications, such as the production of ointments or creams, and cosmetic applications, such as skin protection or the production of shampoos or hair rinses. WO 96/41882 additionally describes compositions, especially compositions for pharmaceutical applications, comprising hydrophobins.
EP-A 1 252 516 discloses the coating of windows, contact lenses, biosensors, medical devices, vessels for performing tests or for storage, ships' hulls, solid particles or frames or chassis of passenger vehicles with a hydrophobin-comprising solution at a temperature of from 30 to 80° C.
WO 03/53383 describes the use of hydrophobin for treating keratin materials in cosmetic applications.
WO 03/10331 discloses that hydrophobins have surface-active properties. For instance, a hydrophobin-coated sensor is disclosed, for example a test electrode to which further substances, for example electroactive substances, antibodies or enzymes, are bonded non-covalently.
WO 2004/000880 presents the coating of surfaces with hydrophobin or hydrophobin-like substances.
WO 01/74864, which relates to hydrophobin-like proteins, also states that they can be used to stabilize dispersions and emulsions.
The use of proteins for phase separation is also known in principle.
For instance, EP-A 05 016 962 describes the use of proteins to improve phase separation of, for example, oil/water or fuel/water mixtures. It is known to those skilled in the art that amphiphilic molecules, depending on the use concentration and surrounding medium, can have either stabilizing or destabilizing effects on phase interfaces.
GB 195,876 discloses a process for breaking water-in-oil emulsions using colloids. The colloids mentioned are, by way of example, proteins such as gelatins, casein, albumin or polysaccharides such as gum arabic or gum tragacanth.
JP-A 11-169177 describes the use of proteins with lipase activity for breaking emulsions.
WO 01/60916 discloses the use of surfactant-free mixtures of at least one water-soluble protein, at least one water-soluble polysaccharide and at least one water-soluble polymer, for example polyethylene oxide, for various uses, also including for the demulsification of crude oil.
However, none of the documents cited discloses the use of hydrophobins for preventing re-emulsification.
The use of proteins has the general advantage that they are naturally occurring substances which are biodegradable and hence do not lead to lasting pollution of the environment.
In many applications on the industrial scale, for example in the separation of crude oil-water emulsions, one important factor is very rapid phase separation and another is the avoidance or prevention of a re-emulsification of the phases. It was an object of the invention to provide an improved process for stabilizing the phases by use of proteins.
According to the invention, this object is achieved by the use of at least one hydrophobin in compositions comprising at least two liquid phases, especially oil and water.